PHARMACOLOGICAL ACTION:Penicillin inhibits, in susceptible bacteria, the synthesis of peptidoglycan, a complex macromolecule which forms one layer of the cell wall of both gram-positive and gram-negative micro-organisms. Peptidoglycan provides rigid mechanical stability by virtue of its highly cross-linked latticework structure. Deprived of its rigid cell wall, the bacterial cell loses the protection it requires because of its high intracellular osmotic pressure. Lysis of the cell membrane and death follows.

Benzathine penicillin G is slowly absorbed from intramuscular depots and produces the longest duration of detectable antibiotic of all the available repository penicillins.

INDICATIONS:For the treatment of infections caused by organisms sensitive to penicillin G.

CONTRA-INDICATIONS:Hypersensitivity to penicillin.

DOSAGE AND DIRECTIONS FOR USE:Treatment of streptococcal infections:A single dose of 600 000 to 900 000 units for children and 900 000 to 1200 000 units for adults is recommended. If necessary, the dose may be repeated as required.

Treatment of pneumococcal infections (except pneumococcal meningitis):One dose of 600 000 units, repeated in 24 hours suffices for mild or moderate cases.
In severe infections, this dose should be repeated every other day until the temperature has been normal for 48 hours.

Treatment of secondary bacterial infections:In many viral infections an injection of 600 000 units is useful in the treatment of complications from secondary bacterial infections.

Treatment of gonorrhoea:One dose of 600 000 to 1 200 000 units is usually effective.

Treatment of syphilis:

TOTAL DOSAGE

PRIMARY AND SECONDARY SYPHILIS

2,4 m units given in a single dose (by injecting 1,2 m units in each buttock).

LATENT SYPHILIS

4,8 m units given in 2 doses, each 2,4 m units (1,2 m units in each buttock), at an interval of 7 days.

6 to 9 m units, administered in doses of 3 m units (1,5 m units in each buttock), at intervals of 7 days.

TOTAL DOSAGE

CONGENITAL SYPHILIS

0,6 to 1,2 m units at intervals of one to two weeks until total dosage is given.

(a) Early congenital syphilis (under 2 years of age

Age

Units per kg of body mass

Average total dose

0-6 months

75 000

1,5 m units

7-12 months

65 000

2,4 m units

12-24 months

60 000

3,0 m units

(b) Late congenital syphilis (over 2 years of age

2 - 4 years

50 000

3,6 m units

5 - 12 years

30 000

40 000

to 4,8 m units

Over 12 years

25 000

30 000

to 6,0 m units

General Prophylaxis.A single dose of 600 000 units is recommended, e.g. administer one day prior to tooth extraction or tonsillectomy.

Prophylaxis in rheumatic fever:For the specific purpose of preventing recurrent attacks of rheumatic fever, a 1 200 000 unit dose is repeated every four weeks. Prophylaxis should be continued indefinitely.

BICILLIN L-A must be administered by deep intramuscular injection in the upper outer quadrant of the buttock. In infants and small children, the midlateral aspect of the thigh may be preferable.

SIDE-EFFECTS AND SPECIAL PRECAUTIONS:In rare instances the injection of penicillin may cause acute anaphylaxis which may prove fatal unless promptly controlled. This type of reaction appears more frequently in patients with previous sensitivity reactions to penicillin, and in those with bronchial asthma or other allergies. Resuscitative medicines such as adrenaline, aminophylline and pressor amines should be readily available for emergency administration.